"Aesthetic function" to show more beautifully, "sensuous function" to give comfortableness, "functionality" such as cosmetic durability and prevention of secondary adhesion, and so on are listed as basic function required to the makeup cosmetic preparation.
The feel of material in case of applying the makeup cosmetic preparation to the face has been generally adjusted by compounding various glossy pigments such as the titanium oxide coated mica pigments in order to achieve aesthetic function. Such titanium oxide coated mica pigments that titanium dioxide layer is formed on the surface of fine flaky mica, have iridescent luster and various interference colors, as described in Cosmetic Ingredients Standard. It is generally manufactured by hydrolyzing inorganic salt solution of titanium such as titanyl sulfate, depositing hydrous titanium dioxide on the surface of mica, and heating it. The interference colors of thus generated titanium oxide coated mica pigments show various colors in accordance with thickness of titanium dioxide coated layer on the surface of mica. However, any object colors thereof are nearly white.
Thereupon, some methods for giving various object colors in the titanium oxide coated mica pigments have been considered. The most general method is to add coloring pigments such as iron oxide, ultramarine blue, chromium oxide, carbon black and carmine on the surface of the generated titanium oxide coated mica pigments. However, this method is defective in decreasing transparency of titanium oxide coated mica. As compared with this, the colored titanium oxide coated mica pigments, which does not spoil transparency of titanium oxide coated mica by doping various metals or metal compounds on mica in titanium oxide coated mica, have been developed.
On the contrary, various functions are recently required to the pigments. As one of such pigments, the pigments having the so-called photochromic property (or phototropic property) are beginning to attract. As the products applying photochromic property, light-modulating glass and color-changeable makeup cosmetic preparation have been developed.
Only single interference color, however, is obtained in the conventional titanium oxide coated mica pigments. Also, when the titanium oxide coated mica pigments are compounded to a foundation, it become nearly white as a whole under sunlight where intensity of light is strong, while it become dark with yellow as a whole in the room where intensity of light is weak. Therefore, it is highly desired to develop the pigment, which has natural color-rendering property in response to intensity of light. The present inventors have studied diligently in order to meet these expectations. Color tones of titanium oxide which is comprised in titanium oxide coated mica are changed in response to intensity of light by giving photochromic property to titanium oxide in titanium oxide coated mica. The present inventors have found that this working emphasizes the interference color that is generated on titanium oxide coated mica and the pigments can function as extremely useful pearl pigment whose observation color is changeable. Thus, the present inventors have developed the titanium oxide coated mica pigment that the observation color changes in response to light and have suggested the pigment in Unexamined Japanese Patent Publication No. Hei 9-165532.
Cosmetic preparations having light-responding color-rendering effect, which respond to intensity of surrounding light have not been developed yet.